The anaerobically induced outer membrance porin, OprG. Transports small neutral amino acids (Kucharska et al. 2015). The 3-d structure is available (Touw et al. 2010).  Essential for normal biofilm formation (Ritter et al. 2012). It is an eight-stranded β-barrel monomer that is too narrow to accommodate even the smallest transported amino acid, glycine, raising the question of how OprG facilitates amino acid uptake (Sanganna Gari et al. 2018). Pro-92 of OprG is important for amino acid transport, with a P92A substitution inhibiting transport and the NMR structure of this variant revealing that this substitution produces structural changes in the barrel rim and restricts loop motions. OprG assembles into oligomers in the OM whose subunit interfaces could form a transport channel, and conformational changes in the barrel-loop region may be crucial for its activity (Sanganna Gari et al. 2018).